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Dopant-Assisted Negative Photoionization Ion Mobility Spectrometry for Sensitive Detection of Explosives

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journal contribution
posted on 02.01.2013, 00:00 by Shasha Cheng, Jian Dou, Weiguo Wang, Chuang Chen, Lei Hua, Qinghua Zhou, Keyong Hou, Jinghua Li, Haiyang Li
Ion mobility spectrometry (IMS) is a key trace detection technique for explosives and the development of a simple, stable, and efficient nonradioactive ionization source is highly demanded. A dopant-assisted negative photoionization (DANP) source has been developed for IMS, which uses a commercial VUV krypton lamp to ionize acetone as the source of electrons to produce negative reactant ions in air. With 20 ppm of acetone as the dopant, a stable current of reactant ions of 1.35 nA was achieved. The reactant ions were identified to be CO3(H2O)n (K0 = 2.44 cm2 V–1 s–1) by atmospheric pressure time-of-flight mass spectrometry, while the reactant ions in 63Ni source were O2(H2O)n (K0 = 2.30 cm2 V–1 s–1). Finally, its capabilities for detection of common explosives including ammonium nitrate fuel oil (ANFO), 2,4,6-trinitrotoluene (TNT), N-nitrobis­(2-hydroxyethyl)­amine dinitrate (DINA), and pentaerythritol tetranitrate (PETN) were evaluated, and the limits of detection of 10 pg (ANFO), 80 pg (TNT), and 100 pg (DINA) with a linear range of 2 orders of magnitude were achieved. The time-of-flight mass spectra obtained with use of DANP source clearly indicated that PETN and DINA can be directly ionized by the ion-association reaction of CO3 to form PETN·CO3 and DINA·CO3 adduct ions, which result in good sensitivity for the DANP source. The excellent stability, good sensitivity, and especially the better separation between the reactant and product ion peaks make the DANP a potential nonradioactive ionization source for IMS.